There is just one thing preventing Elon Musk’s vision from coming true: The laws of physics

When Elon Musk stepped on stage at Tesla’s product-launch event earlier this month, he knew the market’s confidence in Tesla’s brand had sunk to an all-time low since he took over the company a decade ago. So, he resorted to a tactic that should be familiar to anybody who has been following the company: Shock and awe.

While the event was ostensibly scheduled to introduce Tesla’s new semi-truck – a model that won’t make it’s market debut for another two years, assuming Tesla sticks to its product-rollout deadline – Musk had a surprise in store: A new model of the Tesla Roadster that, he bragged, would be the fastest production car ever sold.

Musk made similarly lofty claims about the battery life and performance of both vehicles. The Tesla semi-trucks, he said, would be able to travel for 500 miles on a single charge. The roadster could clock a staggering 620 – more than double the closest challenger.

There was just one problem, as Tesla fans would later find out, courtesy of Bloomberg:None of it was true.

In fact, many of the promises defy the capabilities of modern battery technology.

Elon Musk knows how to make promises. Even by his own standards, the promises made last week while introducing two new Tesla vehicles—the heavy-duty Semi Truck and the speedy Roadster—are monuments of envelope pushing.

To deliver, according to close observers of battery technology, Tesla would have to far exceed what is currently thought possible.

Take the Tesla Semi: Musk vowed it would haul an unprecedented 80,000 pounds for 500 miles on a single charge, then recharge 400 miles of range in 30 minutes. That would require, based on Bloomberg estimates, a charging system that’s 10 times more powerful than one of the fastest battery-charging networks on the road today—Tesla’s own Superchargers.

The diminutive Tesla Roadster is promised to be the quickest production car ever built. But that achievement would mean squeezing into its tiny frame a battery twice as powerful as the largest battery currently available in an electric car.

These claims are so far beyond current industry standards for electric vehicles that they would require either advances in battery technology or a new understanding of how batteries are put to use, said Sam Jaffe, battery analyst for Cairn Energy Research in Boulder, Colorado. In some cases, experts suspect Tesla might be banking on technological improvements between now and the time when new vehicles are actually ready for delivery.

“I don’t think they’re lying,” Jaffe said. “I just think they left something out of the public reveal that would have explained how these numbers work.”

While Jaffe seems inclined to give Tesla the benefit of the doubt, there’s little, if anything, in Musk’s recent behavior to justify this level of credulity. In recent months, Musk has repeatedly suffered the humiliation of seeing his lies and half-truths exposed. For example, the self-styled “visionary” claimed during the unveiling of the Model 3 Sedan that he would have 1,500 copies of the new model ready for customers by the end of the third quarter. Instead, the company managed a meager 260 models as factory-line workers at its Fremont, Calif. factory struggled to assemble the vehicles by hand as the Model 3 assembly line hadn’t been completed.

Increasingly agitated customers who placed deposits with Tesla back in March 2016 have begun asking for refunds, only to be chagrined by the company’s sluggish response. While nobody in the mainstream press has (somewhat bafflingly) made the connection, Tesla revealed earlier this month that it burned an unprecedented $1.4 billion of cash during the third quarter – or roughly $16 million per day – despite Elon Musk’s assurance that Tesla had its “all-time best quarter” for Model S and X deliveries.

And let’s not forget the fiasco surrounding Tesla’s autopilot software. Musk has repeatedly exaggerated its performance claims. And customers who paid more than $8,000 for a software upgrade more than a year ago have been repeatedly disappointed by delays and sub-par performance.

Musk’s exaggerations about the Tesla Roadster were particularly egregious.

Tesla claims that its new $200,000 Roadster is the quickest production car ever made, clocking zero to 60 in 1.9 seconds. Even crazier is the car’s unprecedented battery range: some 620 miles on a single charge. That’s a longer range than any battery-powered vehicle on the road—almost twice as long as Tesla’s class-leading Model S and Model X.

To achieve such power and range, Musk said the tiny Roadster will need to pack a massive 200-kilowatt-hour battery. That’s twice the size of any battery Tesla currently has on the road. Musk has previously said he won’t be making the packs bigger on the Model S and Model X because of space constraints. So how can he double the pack size in the smaller Roadster.

BNEF’s Morsy has a twofold answer. First, he expects Tesla will probably double-stack battery packs, one on top of the other, beneath the Roadster’s floor. That creates some engineering problems for the battery-management system, but those should not be insurmountable. Still, Morsy said, the batteries required would be too large to fit in such a small frame.

“I really don’t think the car you saw last week had the full 200 kilowatt hours in it,” Morsy said. “I don’t think it’s physically possible to do that right now.”

Is it possible that, thanks to incremental improvements in battery density and cost, Musk somehow manages to hit these lofty targets? Perhaps, though, as Bloomberg points out, the fact that Musk is basing these claims on a set of projections that haven’t yet been realized is hardly confidence inspiring.

To be sure, there’s an important caveat to Musk’s claims. While they may be staggeringly exaggerated, there’s still the possibility that incremental improvements in battery technology will make these targets more feasible by the time the models hit the market.

Again, Musk may be banking on the future. While Tesla began taking deposits on the Roadster immediately—$50,000 for the base model—the first vehicles won’t be delivered until 2020. Meanwhile, battery density has been improving at a rate of 7.5 percent a year, meaning that by the time production starts, packs will be smaller and more powerful, even without a major breakthrough in battery chemistry.

“The trend in battery density is, I think, central to any claim Tesla made about both the Roadster and the Semi,” Morsy said. “That’s totally fair. The assumptions on a pack in 2020 shouldn’t be the same ones you use today.”

However, in its analysis of the feasibility of Musk’s claims, Bloomberg overlooked one crucial detail: Back in August, the company’s veteran director of battery technology, Kurt Kelty, unexpectedly resigned to “explore new opportunities,” abruptly ending a tenure with the company that stretched for more than a decade, and comes at a critical time for Elon Musk.

Kelty’s resignation – part of an exodus of high-level executives that is alarming in and of itself – hardly inspires confidence in Tesla’s ability to innovate. We’ve noticed a trend with Tesla: The more the company underdelivers, the more Musk overpromises.